The present invention relates to a fault detection apparatus for a public lighting system of the type having a plurality of lamps, each lamp including an operating and control circuit incorporating fault detection signalling for various portions of the operating and control circuit.
Essentially the term xe2x80x98public lighting systemxe2x80x99 is used here to encompass not exclusively public lighting per se as would be considered to be the meaning of it, but lighting systems for installations whether they be industrial premises, government installations, sporting arenas or the like generally extensive areas, all of which tend to have a large number of lamps operating. Most such lamps have as their source of luminescence a gas discharge tube and this latter term is used to describe the actual source of the light flux in the lamp but obviously other sources could be used.
In this specification the term xe2x80x9cfaultxe2x80x9d is used to indicate an actual fault which causes failure of the system, a fault which causes inefficient operation of the system or indeed an imminent fault that hasn""t as of yet caused any serious malfunction of the system, but which has produced a condition in the system which indicates the possibility that such a fault may arise.
Inevitably lamps fail either due to the simple wearing out of the gas tube or some other failure in the operating and control circuit. Indeed lamps regularly fail prematurely due to incorrect power supply either caused by mains faults or, for example, faulty ballasts or igniters in the operating and control circuit.
Additionally, the lamps often suffer, as they get older, from cycling which causes the lamp to flicker on and off before failing completely and this is an exceedingly undesirable situation to occur.
There are many available lamp control circuits at present, such as, for example, described in European patent Specification No. 0 582 287 (Smeasit S.r.l.). This specification describes an internal auto-diagnostics program for a lamp operating a control circuit, which by means of a modem or radio link reports detected faults to an operations centre. While similar systems are known which provide even adjustment for individual lamps in certain situations, all the systems to date require some form of central host processor which collects and identifies the faults such as that of this European specification. This is relatively complex and expensive and is not suitable for retro-fitting.
What is needed is some relatively simple system or apparatus, whereby maintenance personnel can be alerted to the failure or imminent failure of individual lamps. Ideally, such apparatus should be able to discriminate between the types of failure. For example, the fault could occur in a ballast, which fault would need to be rectified, but would not need to be urgently rectified, while the failure of a bulb or the cycling of a lamp must be rectified as quickly as possible.
Unless some elaborate detection system for faults is incorporated in the public lighting system such as described above the only way of detecting an actual failure of a lamp is by visual inspection of the lamp when it is operating. Potential or imminent failure can only in these circumstances be detected by physically testing the operating and control circuits in situ on a regular basis. The former is extremely expensive to do, but must be done, while the latter though not essential and costly is often necessary as neglect is even more costly.
Thus, there is a need for an apparatus which will allow a fault to be easily efficiently detected at times which are suitable for such detection. Further such an apparatus should be easily incorporated in existing public lighting systems.
Further, there is a need for an apparatus which will allow the fault to be readily easily detected at times that are suitable for such inspection.
According to the invention there is provided a fault detection apparatus for a public lighting system of the type having a plurality of lamps, each lamp including an operating and control circuit incorporating fault detection signalling for various portions of the operating and control circuit characterised in that the fault detection apparatus comprises:
a host interface for connection to the lamp operating and control circuit for the reception of fault detection signals;
a control unit for reception of the fault detection signal; and
an externally visible signalling device connected to the control unit and operable by the control unit to signal the fault.
The invention provides that the signalling device may be a flag or a signalling beacon. Both of these have their advantages. The use of a flag is simple, it is a well known piece of apparatus that is used on many types of switchgear and can be easily seen. However, beacons have other advantages in that they are more clearly visible and can be operated in such a way as to attract attention, such as, for example, by causing them to flash on and off. Thus reporting of a fault does not necessary have to be reported by somebody solely allocated this task, but may, for example, be made by other employees or simply the general public.
Ideally there is provided additional signalling means for sending the fault detection signal to a host control station, which signalling means can provide a short range radio signal for sending the fault detection signal to a remote but relatively near host station.
Indeed the host station does not have to be a central host station, but can be a hand-held device. Thus, for example, maintenance personnel or other employees travelling in a particular area can query detection apparatus within a local area to ascertain whether any are showing a fault or not. The advantage of this is that such a signalling means and associated hand held device need only be fitted to and used with selected lamps in a system which lamps can be chosen depending on their relative importance to the overall lighting system.
In one embodiment of the invention, the fault detection apparatus is housed in a separate plug in unit for connection to the lamp. This allows for retro-fitting.
Ideally the control unit includes analysis means for fault detection signals to identify a particular fault and to cause the signalling device to emit a signal indicating the said fault. The advantage of this is that maintenance personnel can be alerted to the seriousness of the fault or potential fault. In certain cases this might require immediate maintenance attention such as the replacement of the lamp, while in other cases it might be possible simply to note the fault or imminent fault and to plan some routine maintenance.
In another embodiment of the invention the control unit includes means for deactivating the lamp in response to the identification of a fault. The advantage of this is that if the fault is serious then automatically the lamp can be deactivated such as, for example, a lamp that is cycling.
The control unit may incorporate an oscillating circuit or an opto-coupler, both of these are suitable ways of operating the device.
Ideally the signalling device is a high intensity light source, which may, for example, emit a coloured light which can change depending on the fault identified. There are obvious advantages to these.
The control unit includes an additional indicator lamp to signal correct operation of the circuit and the signalling device. The advantage of this is that routine inspection will show if by any chance the fault detection apparatus is inoperative.
Ideally the control unit includes additional control means to only operate the signalling device during certain times. There is absolutely no point in having the signalling device operating in many instances throughout the night and only needs to be operated when people can see it, or are likely to be inspecting it.
Similarly, in one embodiment the control unit includes light sensors to control the level of light during which the signalling device operates. Again this just merely means that the time in which, for example, a beacon can be illuminated is controlled and thus there is no wastage of power. Indeed in relation to this ideally the signalling means operates in a low power mode.